With a typical assembled battery configured by connecting multiple cells in series, adjacent cells are connected in series such that the positive electrode terminal of one of two adjacent cells is connected to the negative electrode terminal of the other of these cells by means of a bus bar. As a connection mechanism that connects the bus bar and the external terminals including the positive electrode terminal and the negative electrode terminal, a connection mechanism is known in which the external terminal is inserted into an opening formed in the bus bar, and a fixation screw is screwed into the end of the external terminal, thereby connecting the external terminal and the bus bar (see Patent document 1).